1. Field of the Invention
The embodiments described herein relate to a system and method for image analysis and in particular to a system and method for the alignment of a plurality of physically scaled mammography images.
2. Description of the Related Art
Medical personnel (e.g. radiologists) examine mammography images to identify various abnormalities in a breast. The task of analyzing mammography images in a digital mammography system typically comprises of using a digital workstation with a display or viewport to align a pair of breast images acquired during a mammography study and comparing breast tissue images of the same side (left/right breast only) or symmetric sides (left and right breasts). The images used for comparison, while of the same object, may be acquired at different times, acquired with different imaging systems and/or acquired using different display settings. As such, medical personnel desire mammography systems that facilitate efficient diagnostic reviews of mammography images, regardless of its provenance, so as to allow them to quickly compare and detect differences between mammographic images and report their findings within clinically acceptable time frames.
Different types of image alignment protocols are employed for displaying mammography images of the breast for comparison. For example, one alignment protocol for images in the cranio-caudal (“CC”) view may involve placing the left and right CC breast views next to each other so that the chest walls will meet on the central vertical axis of the viewport. Similar arrangements, known to those skilled in the art, also exist for medio-lateral oblique (“MLO”) views. Other image alignment strategies include alignment based on anatomical features of the breast. In CC images, for example, the nipple located in each pair of images may be positioned so that they are horizontally aligned, that is, at the same height. For MLO images, either the nipple or pectoralis may be chosen as features used for alignment.
In general, the requirements with respect to mammographic images comparison are: 1) aligning the breast view so as to make the image comparison process easier and more efficient; 2) displaying mammographic images in the same physical scale such that a corresponding real object in each image is observed as the same size; and 3) ensuring that mammographic images are not panned so as to have image areas corresponding to breast tissue being partially outside the viewport or invisible to the examiner.
While currently employed alignment strategies satisfy the above listed requirements, these methods often result in reduced image symmetry, making image comparisons more time consuming. It is preferable to align images to achieve maximum symmetry so that they resemble mirrored images allowing the eyes and brain to quickly identify differences between images. Furthermore, breast features being obscured or missing due to the positioning of the breast during image acquisition may also make alignments relying on those features difficult or impossible. Consequently, a more robust and reliable alignment scheme is desirable. As described herein, a method and system for centering and aligning mammography images may provide greater symmetry is presented, thereby facilitating easier and faster side-by-side comparison.